1. Field of the Invention
The present invention relates generally to the field of petroleum production. More particularly, the invention relates to the collection of petroleum products from a gravity separated well and to the disposal of non-production fluids in such wells.
2. Description of the Related Art
While the need for petroleum products, such as oil and natural gas, has increased in recent years, available reserves for such resources have become ever more scarce. Reserves now being exploited often pose difficult challenges in terms of the efficient removal of the products of interest, typically oil and gas, and the disposal of other fluids, such as water. Producing wells are generally exploited by perforating a wellbore lined with a well casing in one or more regions in which oil is believed to lie, permitting the oil to flow into the wellbore. Depending upon the composition of the underground formations, a significant amount of water may also enter the wellbore along with the oil. Conventionally, the mixture of oil and water (along with any other entrained contaminants) is pumped to the earth's surface where the oil is separated out of the mixture and stored. Separated water may then be reinjected at designated disposal regions within the same or a different well. It should be noted that, as used herein, "oil" is often a mixture of oil and water and "water" is primarily water containing only trace amounts of oil.
In another known technique, the mixture of oil and water is allowed to separate within the well under the influence of gravity. Wells of this type are often referred to as "gravity separated" wells. Because the oil and water are generally immiscible and the oil is lighter than the water, regions of oil and water will eventually form within the well with the oil region overlying the water region. The oil may then be pumped from the oil region, and the water may be removed from the well or directly reinjected at a designated disposal region. In one known arrangement, a pair of pumps are disposed in the well, one within the oil region and another within the water region. The pumps are linked to one another via a sucker rod and actuated by movement of the rod. In another known arrangement, two pumps are coupled to separate drive motors. A pump/motor assembly is then positioned within each of the oil and water regions of the well to pump oil to the earth's surface and water into a disposal region.
Existing techniques for exploiting gravity separated wells suffer from several drawbacks. For example, where separate reciprocating pumps are positioned in the oil and water regions of the well and connected to one another by a sucker rod, the actuating rod itself may be several hundred or even thousands of feet in length, requiring substantial effort to raise and lower the rod to drive the pumps. In addition, such arrangements typically provide only a relatively low flow rate of oil from the well.
There is a need, therefore, for an improved technique for extracting production fluids from gravity separated wells. In particular, there is a need for a system that permits oil to be raised to the earth's surface from an oil region of the well, while disposing of water from a water region, without recourse to pumps separated by large distances within the well.